American will also pay $1.5 million to assume leased equipment that it will continue to use at its engine overhaul facility it still operates at Alliance and jointly runs with Rolls-Royce.

According to the filing, American hired Jones Lang LaSalle to market the property in May 2012 and the firm showed the facility to about 20 prospective firms. American then received two offers for the facility, one from Jet Midwest Group and another from AFW Solutions. American chose to enter into an agreement with AFW Solutions which is backed by Minneapolis-based equity firm, TPG Credit.

American and the city both declined to comment on the lease termination. A court hearing on the agreement is set for September 24.

The maintenance hangar first opened in 1991 with an iconic suspended roof that has no fixed columns holding it up. With its cantilever design, seven wide-body planes standing wingtip to wingtip can fit inside the facility's docks.

American’s initial lease runs until August 2028 with lease extension options until 2089. American pays a base rent of $100 but is also obligated to pay additional charges and expenses for the facility estimated at $7 million annually, the filing said.